The present invention relates to a machine for drying and/or butt-joining "green" or "non-green" wood veneer by continuous contact engagement, said veneer being fed by being unwound or sectioned and offered up in the direction of the wood grain or in a direction perpendicular thereto.
Currently known in this field are drying and jointing machines in which the veneer is restrained and conveyed between two thin metal conveyor belts, heating skids resting by their own weight on the upper belt, which travels faster than the lower belt, which lower belt is supported by fixed heating plates, the heating skids and plates forming successive sections operating at decreasing temperatures.
Also known are machines in which the conveyor belts are formed of a plurality of successive sections that are entirely independent of one another from the standpoints of drive, rate of travel and temperature, each section being formed by a plurality of juxtaposed longitudinal strips and the passage from one section to the next being obtained by a longitudinal interpenetration or offset of the strips.
Likewise known are machines in which the thin conveyor belts are replaced by chains made up of thin or comparatively thick pallets the heating or cooling of which may be effected on the return runs of the chains.
Although the shrinkage phenomena can be reasonably well controlled in the above-mentioned machines, firstly because the upper belt travels faster than the lower belt and secondly because the belts of one section travel faster than the belts of the next section, certain drawbacks are nonetheless inherent in this type of machine.
In the first place, restraining of the veneer is imperfect in the zone of transfer from one section to the next owing to the fact that the veneer is restrained by only half of the chains. Secondly, a risk exists that the veneer may shear at the place where it suddenly passes from one section to the next section, the rate of travel of which is markedly slower. The totality of the forward thrust being transmitted by the fastest section must then be absorbed by the veneer at the level of a single transverse line, which accordingly becomes a preferred line of possible shearing.